I have been a freestyle instructor for a while and kids just like you when you aren't really serious and you just have fun, teach them something important, and show them something really cool. Also, carry hand warmers because they come in handy, and snacks.
1.) Do something fun, come up with a game
2.) If possible, get them into the park or trees, they'll probably have fun there. Well,for an advanced group anyway
3.) Like many people have said, tissues and hand warmers